A souterrain, which is an underground stone-lined tunnel constructed during the early medieval period, typically for storage or refuge, runs beneath the hillside for nearly twelve metres. What makes this one quietly arresting is its location: not tucked into a settlement or hidden in low ground, but close to a hilltop, where the landscape opens up and the structure below becomes easy to forget entirely.

The souterrain at Lehid was recorded by Costello in 1903, who noted its northeast to southwest alignment and its drystone construction, meaning the walls were built without mortar, the stones carefully chosen and placed to hold each other in position. It measures 11.8 metres in length and 1.74 metres in width, making it a substantial example of the type. By the time of that early twentieth-century record it was already partially collapsed, the ceiling giving way in places and the interior becoming less accessible. Souterrains of this kind are scattered across Ireland and are generally associated with ringforts and early ecclesiastical sites, though the precise function of any given example is rarely obvious from the structure alone.